On this memorial day, and exclusive interview with the former top commander in afghanistan. He was drawn into the recent controversy involving cia director david petraeus, who resigned after his affair to paula broadwell. General allen spoke about that and the heroism and sacrifice to the troops to abc's martha raddatz. Reporter: He served in the marine corps for 41 years. His wife, cathy, at his side for yearly all of them. But the last few years of service were toughest. 61 troops you lost. And you said that's a number you will never forget. That's right. I think about it all the time. And there's a mom of reflection about those 561 empty chairs around dinner tables. Reporter: Allen told us he thought long and hard about leaving his post in afghanistan last november, when an investigation was launched into an exchange of e-mails he had with florida socialite jill kell kellk kell kelley. E-mails involving david petraeus. I was notified that e-mails were -- had become known. That was going to require an investigation. Into the appropriateness of the relationship. And I had to reflect on whether I believed I would remain in command. And I believed I could. I felt an obligation, a duty to remain in command. Reporter: Allen was completely cleared of any inappropriate conduct. And says he remains friends with petraeus and his wife, holly. But allen turned down the nato command to take care of cathy, who suffers serious health issues. Together on this memorial day, they are thinking of those who served. This is an opportunity for all americans to think, not just about the troops in uniform today and all, every, single moment. But what everyone has done. The sacrifices of all of our troops for so long, to give this country the quality of life that it has and the freedom we enjoy every, single day. Reporter: Martha raddatz, abc news, virginia. And it was some memorial day

This transcript has been automatically generated and may not be 100% accurate.

Gen. John Allen Cleared in Misconduct Inquiry

The top commander in Afghanistan has been formally cleared of any wrongdoing.

Petraeus Affair: Alleged Mistress Paula Broadwell

Broadwell was writing a biography about the now former CIA director.

{"id":19263524,"title":"Gen. John Allen on Petraeus Scandal","duration":"2:15","description":"The former commander in Afghanistan talks to Martha Raddatz.","section":"GMA","mediaType":"Default"}